1. Field of the Invention
The present invention relates to a transparent touch screen, and more particularly to a top-emitting OLED (Organic Light Emitting Diode) display having a transparent touch panel.
2. Description of the Related Art
OLED display devices are divided into two light emitting modes that are the bottom-emitting mode and the top-emitting mode. The rays emitted from the organic light emitting layer of a bottom-emitting OLED may be blocked by the thin-film transistors (TFT) on the substrate, the aperture ratio is greatly reduced in TFT-OLED. Therefore, the top-emitting OLED is an alternative to improve the ratio of effective light emitting area over total area.
Touch panel is a simple, user-friendly and space-saving input apparatus used in, to name a few, tourist guiding systems, automatic teller machines (ATMs), palm computers, point-of-sale (POS) terminals and industrial control systems.
US Patent Publication No. US 2002/0186208 A1 discloses an electroluminescent (EL) display apparatus with a touch screen. The apparatus includes a transparent substrate, a resistive touch device disposed on one surface of the transparent substrate and an EL display device disposed on the other surface of the transparent substrate. However, the design which the resistive touch device and the EL device are disposed on two corresponding surfaces of the transparent substrate is likely to generate scratches during the manufacturing process. Moreover, the resistive touch device possesses low sensitivity and is not considered a preferred solution in terms of industrial usability.
US Patent Publication No. 2004/0080267 A1 discloses an integrated device of an organic light emitting display (OLED) and a touch screen. The resistive touch device is adopted in this integrated device and is formed on a cover in advance. The combination of the cover and the resistive touch device is then mounted on the organic light emitting display. Due to the low sensitivity of the resistive touch device, scratches are prone to form as a result of excessive pressure exerted on the touch device. Users tend to use assisting tools with sharp tips, such as a pen, in response to the low sensitivity nature of the resistive touch device. Moreover, the resistive touch device integrated with the cover is prone to be affected when the OLED is successively combined.
US Patent publication No. 2004/0090426 A1 discloses a packaged device of an OLED and a touch screen. The resistive touch device is equipped on the surface of the transparent substrate which serves to form the packaged OLED. However, the fabricating method disclosed in such US patent publication is rather complicated, and the lifetime of the organic luminescent material is shortened due to the harsh manufacturing environment of fabricating the resistive touch device. Again, the sensitivity is not a competitive strength of the resistive touch device.
In light of the aforementioned prior arts, a touch panel capable of precisely and sensitively sensing meaningful touches is driven by market force. The utilization of a transparent touch panel further facilitates applications such as input devices integrated with various display screens.